1. Unit 5 Environmental Health I
Unit 5 Environmental Health I. Human health is affected by a large number of risks factors
A. Categories of Human Health Risk
4 Major Categories of Human Health Risk:
Physical
Biological
Chemical
Cultural

2. Physical Risk
Physical – natural disasters such as floods, blizzards, volcanic eruptions, hurricanes and droughts. Also exposure to UV light.

3. Biological Risks
Biological – are risks associated with disease. These hazards result from ecological interactions among organisms.
Disease is a major focus of environmental health
Disease – any impaired function of the body with a characteristic set of symptoms.

4. B. Types of Diseases:
- Infectious Diseases – caused by infectious agent, known as pathogens.
Examples: include pneumonia and sexually transmitted diseases.
Pathogens – disease causing organisms such as viruses, bacteria, fungi, protists and a group of parasitic worms called helminths.
Six types of illness account for 94% of all deaths caused by infection.
Top 3 are cause by the virus that causes the respiratory infection, pneumonia, those caused by AIDS and a variety of pathogens that cause diarrhea.
The next are – TB, malaria and tetanus.

5. HIV Virus
Strep bacteria that causes pneumonia
Giardia Parasite

6. Chronic and Acute Diseases
Chronic – slowly impair functioning of a persons body
Heart disease and most cancers
Acute – rapidly impair the functioning of a persons body
Ebola – a hemorrhagic fever, death occurs in a matter of days.

7. 1. Risk Factors for Chronic Disease in Humans
The World Health Organization (WHO) has come up with the top 10 risks for both rich and poor nations.
Low-in-come countries top ten are associated with poverty and include unsafe drinking water, poor sanitation and malnutrition.
In contrast, malnutrition and poor sanitation are not prevalent risk factors for chronic disease in high-income-countries.

9. II. Infectious Diseases have Killed Large Numbers of People
Epidemic: when a pathogen causes a rapid increase in disease
Vs.
Pandemic: occurs when an epidemic strikes an entire geographic region (Ie. Continent)

10. A. Historically Important Infectious Diseases
Most are associated with poor sanitation and unsafe drinking water
Ex. Cholera, hepatitis, diarrheal diseases
Plague
Malaria
Tuberculosis (TB)

11. Bubonic plague, Black Death
Caused by an infection by bacterium (Yersinia pestis) that is carried by fleas.
Fleas attach to rodents and can be transmitted by handling the rodents/flea bites

14. Symptoms: swollen glands, black spots on skin, extreme pain Estimated hundreds of millions dead; most notable outbreak in 1300’s Europe; early 1900’s Asia Killed 20 in December, 2013 in Madagascar Controlled by modern antibiotics

15. 2. Malaria
Caused by infection from any one of several species of protist in the gnus Plasmodium
Stage 1: inside mosquito; Stage 2: inside of Human
Infections cause recurrent flu-like symptoms
Each Year:
million contract the disease
1 million die from it (mostly children)
Approx. 1,000 US cases (mostly returned from regions where disease is prevalent)

18. Traditional Control Approach : mass DDT spraying proven to be ineffective in many parts of the world; new insecticides can create new problems

19. 3. Tuberculosis
Highly contagious disease caused by a bacterium (Mycobacterium tuberculosis)
Primarily affects the lungs
Spreads when a person coughs and expels the bacteria into the air
Bacteria can persist for several hours and infect a person who later inhales them.

21. TB Symptoms: weakness, night sweats, and coughing up blood one can be infected but not develop the disease estimates are that 33% of the world is infected Each year: 9 million contract the disease; 2 million die

22. TB Treatment: Taking antibiotics for one year
USA: dramatic fall in number of new cases and deaths since 1950’s
If one doesn’t finish the medicine for the full duration: all bacteria aren’t eliminated
1)Pathogen can quickly rebuild its population in the host
2)The last few bacteria are generally more drug-resistant, leading to an evolutionary arms race
20% of Asian and Russian population are infected by these “super strains”
Require newer & stronger antibiotics ($$$$$)

23. The change in risk factors changes as a country moves from low-income to high-income.
Emergent Infectious Diseases
These are infectious diseases that were previously not described or have not been common for at least the prior 20 years.
Since the 1970’s the world ahs seen the emergence of about one new disease a year.

25. B. Emerging Diseases
Many of the emerging disease have come from pathogens that normally infect animal hosts than unexpectedly jump to humans host.
This occurs because of pathogen mutation.
Some of the most high profile diseases that have jumped from animals to humans include HIV/AIDS, Ebola, mad cow, bird flu and West Nile Virus.

26. Emerging Disease
HIV/AIDS – In the 1970’s rare forms of pneumonia showed up it was a symptom of AIDS (Acquired Deficiency Syndrome).
1983 – scientist found the cause of AIDS was HIV (Human Immunodeficiency Virus).
Spread by both sexual contact and IV drug use.
The origin of the virus remained a mystery until 2006, when similar virus found in chimpanzees living in Cameroon.
It is thought that local hunters came into contact with the virus while butchering infected animals.
Today 33 million people in the world are infected with HIV.
25 million have died from AIDS.
(side note; 150 million people in the world are infected with Hepatitis C and more people in the United States die of that then AIDS.

27. 1. HIV
The emergence of new drugs have helped in combating the virus and disease known as AIDS.
Unfortunately many of these drugs are very expensive and not affordable to most people living in low-income countries.

29. HIV Infection
HIV Virus

30. 2. Ebola Hemorrhagic Fever
In 1976 researches first discovered Ebola, a vial disease, first seen in the Democratic Republic of Congo near the Ebola River.
The virus has infected several hundred humans and other primates in Central Africa.
Although the virus is rare, it is of concern because it kills so fast and death rate is high 50-90%
Death occurs within 2 weeks.
Source of the Ebola virus remains unknown

33. 3. Mad Cow Disease also known as Bovine Spongiform Encephalopathy (BSE)
1980’s scientist described a neurologic disease called mad Cow Disease
This disease is different because it is caused by what is called a Prion.
Prions are pieces of brain proteins that mutate and then act as pathogens.
Prions are not well understood and represent a new category of pathogens.
1996 scientist found mad cow disease can be passed to humans who ate meat from infected cattle. Prions can not be destroyed by cooking.

35. Prions
Sick Cow, with Mad Cow

36. Mad Cow
Humans who were infected with mad cow developed what is known as Creutzfeldt-Jacob Disease.
For mad cow to spread, an uninfected cow must consume the nervous system of an infected cow.
1980’s ground-up dead remains of cattle was used as feed and spread the disease.
In Britain, 180,00 cattle died and 166 people as of 2009.
It is estimated that thousands of people are infected but the prion can exist in a human body for many years before death occurs.
Since then Mad Cow has been found in both Canada and United States.
Today it is forbidden to feed animal remains to cattle.

37. Creutzfeldt-Jacob Disease

38. 4. Bird Flu
Bird Flu – Caused by H1N1 virus. Similar to Flu but H1N1 usually infects birds.
2006 a related virus (H5N1) had jumped from birds to people, who had close contact with infected birds. (400 people were infected)
Humans have few defenses against these viruses.
Not easily passed from human to human but if it mutates, that could change.

41. Bird Flu Virus

42. 5. West Nile Virus
Lives in hundreds of species of birds and transmitted among birds by mosquitoes.
Can be transmitted to humans via a mosquito bite.
Causes inflammation of the brain leading to illness and sometimes death occurs.
1999 appeared in New York and spread through most of the United States.

43. West Nile Virus

44. C. The Future of Human Health
Humans face a large number of human health risks but have an excellent understanding of the risk factors that are important and the ways to combat many historical and emerging infectious diseases.
To combat disease in low-income countries, the primary needs are improvement in nutrition, availability of clean water and improved sanitation.
In high-income countries, efforts should be to promote healthier life style, increased physical activities and balanced diet.

45. Chemical Risks
Chemical risks are those associated with exposure to chemicals from natural occurring such as arsenic to synthetic such as pesticides.
Such as disinfectants and pesticides.

46. Cultural Risks
Cultural hazards are those associated with were we live, socioeconomic status and occupation or behavior choices.
Cigarettes
Drugs
Sexually transmitted disease
Diet
Nutrition
Crime

47. III. Toxicology is the Study of Chemical Risks Toxicology
A. Types of Harmful Chemicals
1. Neurotoxins
2. Carcinogens
3. Teratogens
4. Allergens
5. Endocrine Disruptors

48. 1. Neurotoxins These disrupt the nervous system of animals.
Many insecticides are examples of neurotoxins.
Lead and Mercury are examples of neurotoxins.
These are heavy metals that damage kidneys, brain, and nervous system.
Mercury remains a major problem.
Since elimination of lead in gasoline and paint there has been a less exposure in the United States.
Lead remains a serious problem in low-income neighborhoods due to the presence of old lead paint.

49. 2. Carcinogens Carcinogens are chemical that cause cancer.
These chemicals cause damage to cells causing uncontrolled growth or damage genetic material.
Carcinogens that cause damage to genetic material of a cell are called mutagens.
Some well-known carcinogens are asbestos, radon, formaldehyde and chemicals found in tobacco.

50. 3. Teratogens
Teratogens are chemicals that interfere with normal development of embryos or fetuses.
One of the most infamous teratogen was the drug Thalidomide.
Thalidomide was prescribed to pregnant women during the late 1950’s and early 1960’s to combat morning sickness.
It caused mothers around the world to give birth to children with defects.

51. Effects of Thalidomide

52. Teratogens Alcohol is the most common teratogen.
Excessive alcohol consumption reduces the growth of the fetus and damages the brain and nervous system. This is known as Fetal Alcohol Syndrome.

53. 4. Allergens Allergens are chemicals that cause allergic reactions.
Allergens are not pathogens but they are capable of causing an abnormally high response from the immune system.
Response can cause breathing difficulties and even death.
Common allergens include: peanuts, milk, and several drugs such as codeine and penicillin.

54. 5. Endocrine Disruptions
Endocrine Disruptions are chemicals that interfere with the normal functioning of hormones in an animals body.
Example is when hormones from human birth control pills are found in residential sewage and also pesticides that mimic animal hormones.
In waterways contaminated, it has been found that male fish, reptiles and amphibians are becoming feminized.

55. IV. Scientists can determine the concentrations of chemicals that harm organisms
A. Dose-Response Studies: expose animals or plants to different amounts of a chemical and then observe a variety of possible responses including mortality or changes in behavior or reproduction.
Chemicals can be measured as dose or concentration.
Acute studies – are of short duration

57. Dose-response studies most commonly measure mortality as a response.
At the end of a dose-response study the number dead are counted.
The dose at which an effect can be detected is called the threshold.
LD50 – is the abbreviation for Lethal dose that kills 50% of the individuals.
This value is important in assessing the relative toxicity of a chemical.
LD50 studies are conducted on mice and rats and extrapolated to humans.
Sublethal Effects – are studies conducted to determine the effect of a dose that causes 50% of individuals to display the harmful, but nonlethal effect (ED50)

58. 1. Testing Standards
EPA regulates the effects of chemicals on humans and wildlife.
Toxic Substances Control Act of 1976 gives the EPA the authority to regulate many chemicals.
Federal Insecticide, Fungicide and Rodenticide Act of 1996 – regulate pesticides.
For most animals, a safe concentration is obtained by taking the LD50 and dividing it by 10.
For humans, however, the regulatory agencies are much more conservative in setting concentrations.
Rule of thumb for humans, the LD50 is divided by 1000 for humans in order to set a safe standard for humans. This would be a safe concentration.

59. 2. Chronic Studies
Studies conducted for a long period more then just a few days.
Goal is to examine long-term effects of chemicals, including their effects on survival and reproduction.

60. B. Retrospective versus Prospective Studies
Epidemiology is a field of science that strives to understand the cause of illness and disease in human and wildlife populations.
Retrospective Studies – monitor people who have been exposed to a chemical at some time in the past.
Prospective Studies – monitor people who might become exposed to harmful chemicals in the future.
Synergistic Interactions – this is when multiple risks cause more harm than one would expect based on their individual risk.

61. C. Factors that determine concentrations of chemicals organisms experience
1. Routes of Exposure – ways in which an individual might come into contact with a chemical.
For any given chemical, major routes of exposure are limited.
Example – Bisphenol A is a chemical used in manufacturing of plastics (toys, food containers and baby bottles) and may be responsible for early puberty and cancer so knowing this scientist can determine the chemicals solubility and its potential for bioaccumulation.

62. Solubility of Chemicals, Bioaccumulation and Biomagnifications
2. Solubility determines how chemicals move through the environment.
Biomagnification – is the increase in chemical concentration in animal tissues as the chemical moves up the food chain.
Classical example is the case of DDT, and insecticide that has been widely used to kill insect pests in agriculture and to kill mosquitoes that carry malaria.
3. Persistence of a chemical refers to how long the chemical remains in the environment.

63. V. Risk analysis helps us assess, accept, and manage risk.
Environmental hazard – is anything in our environment that can potentially cause harm.
These include: pollutants, chemical contaminants and human activities such as draining swamps, logging and even natural catastrophes such as volcanoes and earthquakes.

64. A. Risk Assessment
Risk assessment seeks to identify a potential hazard and determine the magnitude of the potential harm.
Qualitative and Quantitative.
1. Qualitative Risk Assessment: We make judgments based on perception.
2. Perceived Risks versus Actual Risks – The perception that certain behaviors or activities carry a high risk does not always match the reality

65. Risk Assessment
3. Quantitative Risk Assessment: This is the most common approach to conducting quantitative risk assessment and can expressed with a simple equation Risk = probability of being exposed to a hazard X probability of being harmed if exposed This uses data, from acute and chronic dose responses as well as retrospective and prospective studies.

66. Actual Risk Data in the USA (Based on Quantified Cause of Deaths)

67. 4. A Case Study in Risk Assessment
1940s-1970s: Electrical component manufacturers dumping Polychlorinated biphenyl (PCBs) into rivers
EPA discovered this action and began a risk assessment

68. EPA Risk Assessment on PCBs
Which level of PCBs caused cancer?
They exposed lab rats to different concentrations to determine LD50 and assessed industry retrospective studies to determine these levels
2) Determine which levels of contamination people were most likely to experience
Examined data on current concentrations in the air, soil, and water and considered the half-life of the chemical
% of PCB contact was determined to be relatively high
Other exposure: eating fish, drinking water, contaminated air

69. EPA Risk Assessment on PCBs
3) The final result:
Risk of eating contaminated fish was greater than that of water, or air
Signs were posted on local waterways alerting anglers of this danger and to not consume harvested fish
With limited fish consumption, it was now determined that PCB risk was to be relatively low
It was recommended that the Hudson River by dredged to remove the toxins that settled to the bottom of the river

70. B. Risks Acceptance
Once a risk assessment is completed the next step is determining risk acceptance – the level of risk that can be tolerated.
C. Risk Management – This is the third step in risk analysis. This seeks to balance possible harm against other considerations.
Risk Management – integrates the scientific data on risk assessment and the analysis of acceptable levels of risk with a number of additional factors including economic, social, ethical and political issues.

71. D. Worldwide Standards of Risk
Innocent-until-proven-guilty principle – based on the philosophy that a potential hazard should not be considered a hazard until the scientific data can definitively demonstrate that a potential hazard actually causes harm.
Precautionary principle – based on the philosophy that when a hazard is plausible but not yet certain, we should take actions to reduce or remove the hazard.

72. 1. International Agreements on Hazardous Chemicals
2001 – 127 nations gathered in Stockholm, Sweden to reach an agreement on restricting the global use of some chemicals.
Stockholm Convention – produced a list of 12 chemicals to be banned, phased out, or reduced.
Dirty Dozen – include: PCB’s, DDT all chemicals that are known endocrine disruptors.
REACH (Registration, Evaluation, Authorization, and restriction of CHemicals) In 2007, 27 nations of the European Union put forth this agreement on how chemicals should be regulated.
embraces the precautionary principle by putting more responsibility on chemical manufactures to confirm that chemicals used in the environment pose no risk to people or the environment.